GIA Hong Kong Identifies 10 CVD Synthetic Diamonds

RAPAPORT... The Gemological Institute of America (GIA) reported in its July issue of Gems & Gemology monthly eBrief that 10 synthetic diamonds grown by the chemical vapor deposition (CVD) were submitted to GIA Hong Kong in June. The stones appeared comparable to their top-quality natural counterparts, according to GIA.

The article stated: ''These round brilliants ranged from 0.30 to 0.35 carat, with F–H color grades. Microscopic examination showed no fractures or inclusions, but did reveal weak graining and tiny pinpoints. Accordingly, their clarity grades ranged from VVS1 to VVS2, and one sample received a VS1. The specimens were essentially inert to long-wave UV radiation and displayed a very weak yellow to green-yellow fluorescence to short-wave UV.''

GIA also found that infrared absorption spectroscopy identified all 10 synthetic diamonds as type IIa, but they lacked IR features that are commonly recorded in CVD synthetics, according to the lab. However, photoluminescence spectra collected at liquid-nitrogen temperature with various laser excitations showed very strong [Si-V]0 emissions, as well as strong peaks from N-V centers and an H3 emission. The DiamondView revealed moderate green fluorescence (attributed to the H3 optical center) and typical CVD growth striations. Weak blue phosphorescence was also observed in each stone in the DiamondView, according to the eBrief.